Asynchronous interfaces represent a widely used format for communications between components in a system. Such interfaces are especially useful when the various components with which communication is to be established have different clock domains. An asynchronous interface can send data signals without sending an accompanying clock signal. The sender of the asynchronous data may have one clock domain, and the receiver may have a different clock domain and still be able to correctly receive the asynchronous data. Specifically, components with different clock domains do not need additional resources for clock conversion to synchronize to any transmitted clock signals.
The operation of an asynchronous interface depend on the use of timing characteristics such as set-up times and hold times. These timing characteristics specify important tolerances in the timing of signals. The design of a system that utilizes an asynchronous interface takes such tolerances into account to ensure that components can correctly transmit and receive asynchronous signals in spite of factors such as non-uniform propagation delays, variances in clock speeds of different components, etc.
Timing considerations affect the layout of components and interconnections within a system implemented, for example, in a semiconductor device. The layout may need to be created in view of the timing of asynchronous signals, so that interface communications can be conducted properly. The design of a system employing an asynchronous interface is thus intrinsically tied to the timing characteristics associated with the interface.
Indeed, the configuration of a system including its physical layout is often planned around fixed timing characteristics. While this allows the system to be safely designed to meet requirements on signal timing, the resulting design is one that is relatively inflexible. Changes to the design may lead to timing violations.
Just as an example, a system may be designed to provide asynchronous interface communications for a particular group of components. The timing characteristics associated with the asynchronous interface may be set at values that are optimized while accommodating the various clock speeds of the existing components. If the design of the system is modified by inserting a new component into the system, the original timing characteristics may no longer be appropriate. For instance, the newly inserted component may have a much slower clock speed that requires the timing characteristics to be adjusted. In this situation, the design of the entire system may need to be re-worked because other portions of the system may be configured to rely upon the original timing characteristics.
Alternatively, the designed of the system may also be modified by deleting one of the existing component. It may be the case that without the deleted component, the timing characteristics can be improved to speed up the asynchronous interface. After all, the interface no longer has to accommodate the deleted component. Thus, the original timing characteristics may be optimized to new values. Again, the design of the entire system may need to be re-worked because other portions of the system may be configured to rely upon the original timing characteristics.
In yet another example, the system may be updated such that one or more components within the system may run at new clock speeds. The original timing characteristics may no longer be optimal or even functional given the new clock speeds used. Thus, the timing characteristics may need to be changed from their original values. Once again, a change of the timing characteristics may lead to a redesign of the entire system.
Thus, timing considerations for an asynchronous interface can have a tremendous impact on the design of an overall system. At the same time, the cost of redesigning systems, e.g., changing the physical layout of a semiconductor device, can be quite considerable and even prohibitive. As such, there exists a significant need for a manner of specifying timing characteristics such that expensive system redesigns can be avoided.